A PROCESS OF IRON MAKING USING SINTER FINES

Abstract

A process of iron making and, in particular, to a process of iron making using sinter fines which is directed to selective and advantageous use of sinter fines (size below 8mm.) which can not be recycled in sinter plant and cause disposal and environmental problems. The invention involving beneficial utilization of sinter fines would thus favour increasing the hot metal productivity upto about 4% and also help controlling the process parameters of iron manufacture involving melter-gasifier more uniformly. The process of the invention involving such advantageous application of sinter fines can be adapted in any conventional iron making furnace comprising melter-gasifier such as those used in the Corex and Finex processes. More importantly, the process of iron making according to the invention is also directed to reduction in fuel rate, flux consumption and possible replacement of upto about 25% of the costly pallets used in iron manufacture. The process would make iron making such as following Corex and Finex more effective and user friendly with improved productivity.

Full Text

FORM 2 THE PATENT ACT 1970 (39 OF 1970) & The Patent Rules, 2003 COMPLETE SPECIFICATION (See Section 10 and Rule 13)1 TITLE OF THE INVENTION :A PROCESS OF IRON MAKING USING SINTER FINES2 APPLICANT (S)Name : JSW Steel Limited.Nationality : An Indian Company.Address : Jindal Mansion, 5-A, Dr. G. Deshmukh Marg, Mumba- 400 026, State of Maharastra, India.3 PREAMBLE TO THE DESCRIPTIONCOMPLETEThe following specification particularly descibes the invention and the manner in which it is to be performed.

FIELD OF THE INVENTION
The present invention relates to a process of iron making and, in particular, to a process of iron making using sinter fines. Importantly, the process of the invention is directed to selective and advantageous use of sinter fines (size below 8 mm.) which can not be recycled in sinter plant and cause disposal and environmental problems, whereby it would be possible to increase the hot metal productivity upto about 4% and also help controlling the process parameters of iron manufacture involving melter-gasifier more uniformly. The process of the invention involving such advantageous application of sinter fines can be adapted in any conventional iron making furnace comprising melter-gasifier such as those used in the Corex and Finex processes. More importantly, the process of iron making according to the invention is also directed to reduction in fuel rate, flux consumption and possible replacement of upto about 25% of the costly pallets used in iron manufacture. The process is thus directed to make iron making such as following Corex and Finex more effective and user friendly with improved productivity.
BACKGROUND ART
It is well known that the major iron bearing feed to Blast Furnace (BF) is sinter. It is an agglomerate of iron ore, form on heating to temperatures in the range of 1300 to 1350°C. The product sinter is known to be crushed and then screened at sinter plant and BF, to use +5 mm sinter in BF. The generation of sinter fines below 8 mm is upto 30%, which is recycled back to sinter plant. The sinter plant process allows about 15-20% of sinter fines, above which it deteriorates the sinter quality and also increases the cost of production. The remaining sinter fines which can not be recycled in sinter plants cause disposal and environmental problems.
COREX® is a well known smelting reduction process based on lumpy ore and/or pellets and coal. It basically consists of (i) reduction shaft and (ii) melter-gasifier. The raw materials i.e., pellets, iron ore, coke and fluxes are continuously charged into the reduction shaft. The hot DRI alongwith partially calcined fluxes from shaft are fed into the melter-gasifier. Additionally, non-coking coal is charged. Oxygen is blown through the tuyeres which gasifies the coal and generates CO. The remaining reduction and meiting occurs in the melter. The hot metal and slag are then taken out from the bottom.
The production of corex thus depends on the performance of the reduction shaft so the fine ore portion in the ore burden charged into the reduction shaft is limited in order to maintain uniform gas penetration and stable operation of the reduction shaft.

Some recent developments in the art provide process of injecting fine iron ore into melter-gasifier which is stated to have the potential to use upto 25% of fine ore and iron containing fines in the COREX® process through the melter-gasifier. This is stated to also lead to an increased flexibility, enlarge capacity and improved economics of the COREX® process. Additionally, such process also allows the use of ore fines from material handling and direct use of iron bearing fines of the metallurgical plant. However, in such a process the size of the fine ore which can be used was limited to 6-12 mm. Any use of fines below 6 mm led to increase in dust load and related jamming of dust recycling system.
It would be thus apparent from the above that while improvement to the COREX® process has been suggested which can make good use of fine ore and iron containing fines but there remain limitations in use of fines above 6 mm to avoid increase dust loading and jamming of dust recycling system and thus there continues the need to provide for alternative which can make the COREX® process more efficient and yet be cost effective, environment friendly and importantly serve in improved production of hot metal.
OBJECTS OF THE INVENTION
It is thus the basic object of the present invention to provide for improvement in iron making which would on one hand favour cost effective and improved productivity of metal involving melter-gasifier based iron making furnaces and at the same time on the other hand ensure effective utilization of sinter fines which can not be recycled in sinter plant and are known to cause disposal and environmental problems.
Another object of the present invention is directed to process of iron manufacture involving melter-gasifier furnace with increased productivity and reduced fuel rates.
A further object of the present invention is directed to a process of iron manufacture involving melter-gasifier which would involve reduced flux consumption and reduced requirement of cost extensive pellets.
Another object of the present invention is directed to a simple and cost effective process of manufacture of iron involving the use of sinter fines thereby avoiding the problem of recycling, and disposal of such fines and yet facilitate maintaining the gas composition

and HM quality thereby favouring wide scale application and use of the process in such iron making.
Yet another object of the present invention is directed to improvement in iron making by way of effective utilization of sinter fines below 8 mm generated from sintering processes which otherwise constitute a waste difficult to dispose and affected environmental concerns.
A further object of the present invention is directed to process for iron making involving iron making furnaces such as melter-gasifier which would allow use of other iron bearing waste alongwith sinter fines in melter gasifier to generate quality metal with improved productivity.
Yet further object of the present invention is directed to development in the process of iron making involving melter-gasifier furnaces such as those used in Corex, Finex and the like which would favour increasing the productivity of such processes and also take care of problems of recycling of sinter fines generated in sinter plants which are known to cause disposal and environmental problems.
SUMMARY OF THE INVENTION
Thus according to the basic aspect of the present invention there is provided a process of iron making using sinter fines comprising:
involving iron making furnace comprising of melter -gasifier with desired charge; and charging undersized iron bearing sinter fines of size upto 8 mm directly into the melter-gasifier whereby the available heat at the top of the fixed char bed in said melter -gasifer enables reduction of the fines and thereby increase hot metal productivity.
In accordance with a preferred aspect the process of the invention comprises a COREX smelting reduction iron making process comprising of a reduction shaft and a melter-gasifer wherein the raw materials comprising pellets, iron ore, coke and fluxes are continuously charged into the reduction shaft with injection of reduction gas at about 850°C therein whereby the metallic get reduced to over 70% metallization by gases from the melter-gasifer;

the hot DRI alongwith the partially calcined fluxes from the shaft are fed into the melter-gasifer at around 800°C and additionally sinter fines of size upto 8mm alongwith coal line charging of coal, coke quartz and iron ore is charged in said melter-gasifer with blowing of oxygen to gasify the coal and generate CO maintaining a dome temperature of about 1050°C to ensure cracking of volatile matter released from coal , said addition of sinter fines via coal line directed to increase the hot metal production and assist in controlling the process parameters more uniformly.
Thus as apparent from the above the process of iron making using sinter fines of the invention can be utilized in any melter-gasifer such as the melter-gasifiers provided in Corex or Finex process or any other melter-gasiler based iron making furnace.
In the above process of iron making using sinter fines the addition of the sinter fines can be attended preferably via the coal line.
In accordance with another aspect in the process of iron making using sinter fines of the invention, the addition of sinter fines in the melter-gasifer can be done by substitution of total iron bearing material upto about 15%.
The sinter fines suitable for use in the process of the invention preferably comprise size and chemical analysis of :

Size analysis
+ 8mm, % Up to 15
-8 mm, % Up to 100
- 6.3mm, % up to 100
-1 mm, % up to 25
Chemical analysis
Fe(t), % 50 to 59
SiO2. % 3.5 to 7.5
Al2O3. % 2.0 to 5.0
CaO, % 5.0 to 15.0
MgO, % 0.5 to 3.0
Advantageously, the process of iron making using sinter fines of the invention can have the sinter fines mixed with other iron bearing waste such as iron ore fines from yards and pellet fines which together can be charged in the melter-gasifer.
Importantly, such addition of sinter fines facilitate the decrease in the flux consumption and thereby the calcinations load in the reduction shaft in the iron making process.

According to an aspect of the invention in the above process of iron making using sinter fines the coal line to the melter gasifier comprise bunkers for feeding charge including coal, coke, quartz , limestone-dolomite fines and said sinter fines. Preferably, one of the bunkers is dedicated for feeding of the sinter fines and the sinter fines from this bunker are discharged to a weigh bin through a vibro feeder, said weigh bin providing for discharge of the sinter fines as per requisite amount into the coal batch, said coal batch along with the sinter fines operatively connected to the lock hopper for selective feeding into the melter-gasifier.
Thus the above process provides for advantageous use of the sinter fines below 8mm generated from sinter process and which cannot be recycled in the sinter plant.
It is thus possible by way of the above disclosed process of iron making involving selective and advantageous use of sinter fines which would enable increasing the productivity and reducing the fuel rate and also flux consumption. Advantageously, the process of iron making in melter-gasifier of the invention utilizing sinter fines would favour replacing upto 25% of the costly pellets without requiring any change in gas composition and HM quality.
Thus, the above process of the invention provides for effective utilization of sinter fines below 8 mm generated from sintering process which are otherwise problematic waste and difficult to handle. Moreover, the sinter fines which are effectively utilized in the process according to the invention also allow the use of other iron bearing waste mixed alongwith the sinter fines in melter-gasifier. The process of the invention would thus serve for better cost effective: production iron involving sinter fines in melter-gasifier such as in the Corex, Finex and like iron manufacturing.
The details of the invention, its objects and advantages are explained hereunder in greater detail in relation to non-limiting exemplary illustration of the process as per the following accompanying figures:-
BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES:
Figure 1 : is a schematic illustration of a Corex system;

Figure 2: is an illustration by way of line diagram of the coal line used for charging sinter fines into melter-gasifier in accordance with the present invention;
Figure 3: is a representation of the effect of sinter fines use in accordance with the invention on the Corex melting rate.
DETAILED DESCRIPTION OF THE ACCOMPANYING FIGURES
Reference is first invited to accompanying Figure 1 which illustrates the Corex system. As shown in Figure 1 the Corex basically involves the reduction shaft (RS) and the melter-gasifier (MG). In the reduction shaft (RS), pellets/lump ore (1) and fluxes such as lime stone, dolomite (2) are fed from the top. The reducing gas from the melter-gasifier (MG) is fed into the reduction shaft (RS) through the bustles (3). Six numbers of screws are provided to discharge reduced iron from the reduction shaft (RS) into the melter-gasifier (MG). The melter-gasifier (MG) is provided with the fixed char bed (9) and the coal line for charging coal, coke, quartz, iron ore and sinter fines is identified by reference (11) while the tap hole for tapping slag and hot metal at the bottom is marked (10). The Figure further shows the provision of generator gas ducts (6) total 4 nos., hot gas cyclone (HGC) for separating dust from the gas (7) and a lower bust bin (8) to catch dust separated by (HGC) before injecting through dust burners.
More specifically, in the above illustrated COREX® the same is a smelting reduction process based on lumpy ore and/or pellets and coal. As shown it consists of two reactors; (i) the reduction shaft (ii) the melter-gasifier. The raw materials i.e. pellet, iron ore, coke, and fluxes are continuously charged into the reduction shaft. Reduction gas is injected through the bustle at 850°C. The gas moves in the counter current direction to the top of the shaft and exits at around 250°C. The metallics get reduced to over 70% metallization by gases from melter-gasifier. The hot DRI along with partially calcined fluxes from shaft are fed into the melter-gasifier at around 800°C. Additionally, non-coking coal is charged. Oxygen is blown through the tuyeres which gasifies the coal and generate CO. The dome temperature is maintained at ~1050°C, which ensures cracking of volatile matter released from the coal. The gas from the melter-gasifier is cooled to 850°C through the addition of cooling gas before feeding to the reduction shaft. The remaining reduction and melting occurs in the melter. The hot metal and slag are taken out from bottom.

Importantly, the present process is directed to make advantageous use of the sinter fines which usually cannot be recycled in sinter plants and cause disposal and environmental problems. Thus, in accordance with the present invention it is proposed that undersized iron bearing sinter fines (size below 8 mm) be effectively utilized and charged directly into the Corex melter-gasifier (MG).The sinter fines used for such feeding in the Corex melter-gasifier (MG) involved had the size and chemical analysis as detailed hereunder:

Size analysis
+ 8mm, % 10
-8 mm, % 90
- 6.3mm, % 70
-1 mm, % 15
Chemical analysis
Fe(t), % 54.9
SiO2. % 5.91
Al2O3. % 3.47
CaO, % 9.88
MgO, % 2.00
The addition of sinter fines in the melter-gasifier (MG) is preferably attended involving the coal line used for charging the melter-gasifier as shown in Accompanying Figure 2.
As apparent from said Figure 2, in the coal line there are total 5 bunkers for feeding coal, coke, quartz and lime stone-dolomite fines of which one of the bunker is dedicated to sinter fines storage. The sinter fines from this bunker are discharged to the weigh bin (2) through a vibrofeeder (1). These weigh bin discharges the sinter fines as per the requisite amount into the coal batch. The coal batch alongwith the sinter fines is sent to coal lock hopper which is then fed to the melter-gasifier via dosing belt (3) and conveyor (4) as clearly shown in said Figure 2.
The effect of such use of sinter fines in the Corex melting rate in melter-gasifier in accordance with the invention was studied and the results were noted as represented in accompanying Figure 3.
As apparent from Figure 3, the addition of these sinter fines via the coal line increased the hot metal productivity by 4% and helped in controlling the process parameter more uniformly.

It is further studied that on a monthly average basis upto 15% of the total iron bearing material could be substituted by sinter fines addition. This could be achieved due to no moisture and low - 1 mm fraction in the sinter fines coupled with its high reducibility.
As already mentioned the sinter fines mixed with other iron bearing waste such as iron ore fines from yard and pellet fines can also be charged into the melter-gasifier. It is also found that advantageously, the sinter fines helped decrease the flux consumption and thereby the calcinations load in the reduction shaft.
More specifically, studies conducted on the processes involving such use of sinter fines have revealed that sinter fines were advantageous for Corex and specifically achived the following: (i) increased the production by 4% (ii) reduced fuel rate above 20 kg/thm (iii) reduced flux consumption by 50 kg/thm (iv) possible replacement of up to 25% of the costly pellets;(v) there was no change in gas composition and HM quality (vi) favoured effective utilization of sinter files below 8mm generated from sintering process which otherwise was a problematic waste to handle and for the environment (vii) allows use of other iron bearing waste to be mixed alongwith the sinter fines into the melter-gasifier and (viii) allows use of sinter fines into furnace involving melter-gasifier such as the Corex.Finex etc. Thus the process of the invention would serve increasing the production in melter-gasifier units such as those used in Corex and Finex through effective and advantageous use of sinter fines in such processes for cost-effective production of iron and benefical use of sinter fines and avoiding problems of its disposal from sinter plants and the like.

WE CLAIM:
1. A process of iron making using sinter fines comprising:
involving iron making furnace comprising of melter -gasifier with desired charge; and charging undersized iron bearing sinter fines of size upto 8 mm directly into the melter-gasifier whereby the available heat at the top of the fixed char bed in said melter -gasifer enables reduction of the fines and thereby increase hot metal productivity.
2. A process of iron making using sinter fines as claimed in claim 1 wherein the melter -gasifer comprises of melter-gasifiers provided in Corex or Finex process or any other melter-gasiler based iron making furnace.
3. A process of iron making using sinter fines as claimed in anyone of claims 1 or 2 wherein the addition of the sinter fines are via the coal line.
4. A process of iron making using sinter fines as claimed in anyone of claims 1 to 3 wherein the addition of sinter fines in the melter-gasifer is done by substitution of total iron bearing material upto about 25%.
5. A process of iron making using sinter fines as claimed in anyone of claims 1 to 4 wherein the sinter fines preferably comprise size and chemical analysis of :

Size analysis
+ 8mm, % Upto 15
-8 mm, % Up to 100
- 6.3mm, % up to 100
-1 mm, % up to 25
Chemical analysis
Fe(t), % 50 to 59
SiO2. % 3.5 to 7.5
Al2O3. % 2.0 to 5.0
CaO, % 5.0 to 15.0
MgO, % 0.5 to 3.0
6. A process of iron making using sinter fines as claimed in anyone of claims 1 to 5 wherein sinter fines mixed with other iron bearing waste such as iron ore fines from yards and pellet fines are also charged in the melter-gasifer.
7. A process of iron making using sinter fines as claimed in anyone of claims 1 to 6 wherein the addition of sinter fines facilitate the decrease in the flux consumption and thereby the calcinations load in the reduction shaft in the iron making process.

8. A process of iron making using sinter fines as claimed in anyone of claims 1 tc 7 wherein the coal line to the melter gasifier comprise bunkers for feeding charge including coal, coke, quartz , limestone-dolomite fines and said sinter fines.
9. A process of iron making using sinter fines as claimed in claim 8 wherein one of the bunkers is dedicated for feeding of the sinter fines and the sinter fines from this bunker are discharged to a weigh bin through a vibro feeder, said weigh bin providing for discharge of the sinter fines as per requisite amount into the coal batch, said coal batch alongwith the sinter fines operatively connected to the lock hopper for selective feeding into the melter-gasifier.
10. A process of iron making using sinter fines as claimed in anyone of claims 1 to 8 wherein the sinter fines comprise sinter fines below 8mm generated from sinter process and which cannot be recycled in the sinter plant.
11. A COREX smelting reduction iron making process comprising of a reduction shaft and a melter-gasifer wherein the raw materials comprising pellets, iron ore, coke and fluxes are continuously charged into the reduction shaft with injection of reduction gas at about 850°C therein whereby the metallic get reduced to over 70% metallization by gases from the melter-gasifer; the hot DRI alongwith the partially calcined fluxes from the shaft are fed into the melter-gasifer at around 800°C and additionally sinter fines of size upto 8mm alongwith coal line charging of coal, coke quartz and iron ore is charged in said melter-gasifer with blowing of oxygen to gasify the coal and generate CO maintaining a dome temperature of about 1050°C to ensure cracking of volatile matter released from coal , said addition of sinter fines via coal line directed to increase the hot metal production and assist in controlling the process parameters more uniformly.
12. A process of iron making using sinter fines in melter gasifier such as in COREX FINEX melter-gasifer based iron making substantially as here in described and illustrated with reference to the accompanying examples and figures.

ABSTRACT
TITLE : A PROCESS OF IRON MAKING USING SINTER FINES
A process of iron making and, in particular, to a process of iron making using sinter fines which is directed to selective and advantageous use of sinter fines (size below 8 mm.) which can not be recycled in sinter plant and cause disposal and environmental problems. The invention involving beneficial utilization of sinter fines would thus favour increasing the hot metal productivity upto about 4% and also help controlling the process parameters of iron manufacture involving melter-gasifier more uniformly. The process of the invention involving such advantageous application of sinter fines can be adapted in any conventional iron making furnace comprising melter-gasifier such as those used in the Corex and Finex processes. More importantly, the process of iron making according to the invention is also directed to reduction in fuel rate, flux consumption and possible replacement of upto about 25% of the costly pallets used in iron manufacture. The process would make iron making such as following Corex and Finex more effective and user friendly with improved productivity.
FIGURE 2.